Not Applicable.
1. Field of the Invention
The present invention relates generally to logging while drilling (LWD) technologies. More specifically, the invention relates to downloading data stored in the memory of LWD devices. More specifically still, the invention relates to a data dump probe that downloads data from LWD devices.
2. Background of the Invention
Modern petroleum drilling and production operations demand a great quantity of information related to parameters and conditions down hole. Such information typically includes characteristics of the formations traversed by the well bore, in addition to data relating to the size and configuration of the bore hole itself. The collection of information relating to characteristics of formations down hole is commonly referred to xe2x80x9clogging.xe2x80x9d Logging has been known in the industry for many years as a technique for providing information regarding the particular formation being drilled and can be performed by several methods.
One such logging method is convention wire-line logging. In wire-line logging a probe is lowered into the bore hole after some or all of the well has been drilled, and the probe is used to determine certain characteristics in the formations traversed by the bore hole or the bore hole itself. While wire-line logging is useful in assimilating information about down hole formations, before a wire-line logging tool can be run in the well bore, the drill string and bottom hole assembly must first be removed resulting in considerable cost and loss of drilling time for the driller (who typically is paying daily fees for the rental of equipment).
Because of the limitations associated with wire-line logging, there recently has been an increasing emphasis on the collection of data during the drilling process itself. By collecting data during the drilling process, without the necessity of removing the drilling assembly to insert a wire-line logging tool, data regarding the down hole formations can be collected more economically. Data collected during the drilling operation must either be relayed to the surface or stored until the logging device is brought back to the surface. Given the relatively slow data rates achievable in communicating from down hole logging and measuring devices to surface computers, storing the data collected may be the only option for the majority of data.
Several types of logging devices, or LWD tools, are used by the industry and each tool may require varying amounts of internal memory. For example, a xe2x80x9cgammaxe2x80x9d tool requires comparatively little memory; whereas, an acoustic or sonic tool may require a significant amount of memory, approaching 250 Megabytes, to have the capability to store all the information required during a drilling run. Other down hole tools may also include a resistivity tool, a caliper tool, and a directional tool. Information gathered by the directional tool is needed relatively real time with the drilling process, and therefore, the information gathered by a directional tool is generally sent from down hole to surface computers using known techniques such as by transmitting mud pulses to the surface at approximately a 1 Hz baud rate.
On a tool that stores data from a drilling run, some method must exist to extract the data stored in the tool. Currently, information obtained by a LWD tool is stored in memory within the tool itself until the logging tool is brought to the surface. Upon being lifted to the surface, the data is extracted. Referring to FIG. 1, there is depicted a prior art structure for downloading data stored in the memory of a logging tool. Shown in FIG. 1 is a drill string 10 which comprises a LWD tool 12 and drill bit 14, a drilling table 16, surface computer 18, download cable 20 and connector 22.
The LWD tool 12 is raised to the surface of the earth after a drilling run. Once the LWD tool 12 is raised slightly above the drill table 16, an operator stretches download cable 20 to the LWD tool 12 and thereby couples the surface computer 18 to the LWD tool 12 via the connector 22. While this operation seems relatively simple, several practical problems exist.
On most drilling rigs, especially drilling platforms on the ocean, space is a commodity and therefore the surface computer may not, indeed most likely is not, close to the LWD tool 12. Another consideration is the environment of the download process. Drilling rigs and drilling platforms, especially on the drilling table 16, are generally explosive environments. Small sparks could create a fire or explosion. The computer may potentially create sparks, and thus may not be permitted on the rig floor. Consequently, the surface computer may be several floors and hundreds of feet from the drilling table 16. Further, plugging an unplugging electrical connectors may created sparks in the potentially explosive environments and, for this additional reason, use of download cables 20 on or near the drilling table 16 have the added disadvantage of a potential fire or explosion hazard.
As one of ordinary skill in the art will realize, the information rate a cable may accurately transmit decreases as the length of the cable increases. This means, for the system described in FIG. 1, that as the surface computer is placed further from the logging tool, the download rate decreases and therefore the time required to download increases as the cable length increases.
An additional factor that decreases data download rates is electrical noise. A drilling rig has many pumps and motors associated with the drilling process which create significant electrical noise. Because the download cable 20 winds in and around the drilling rig to get to the surface computer, it becomes an antenna for receiving electrical noise. Electrical noise further decreases the data rate of the cable. Given all these conditions, the typical data rate for the cable 20 of the related art may be at or near 80 kilo-baud.
Further, with data rates associated with the related art methods of downloading information in the 80 kilo-baud range, downloading information from a memory intensive logging device, e.g. an acoustic probe, may take in excess of thirty minutes. Various techniques exist to insure that no data errors occur in the digital communication, but these techniques are not infallible. On occasion, a download may occur having errors that precipitate a second download of the same information, and possibly even a third, until the information is exchanged error free. In these instances when an error occurs and the process of downloading is repeated, significant rig time is lost to the download process.
As the demand for LWD data increases many companies have begun placing multiple logging devices in the drill string for measuring multiple parameters as part of the logging while drilling process. The problems experienced with the download cable 20 as described in reference to FIG. 1 increase substantially as the number of logging devices, with internal memories that require downloading on the surface, increase. Referring to FIG. 2, there is indicated one possible structure for downloading data contained in multiple logging devices. As indicated in the figure, the envisioned method is to have a breakout box 15 somewhere near the drilling table 16, and from this breakout box having an individual download cable 20A, 20B, 20C for each and every logging device in the drill string. Each download cable 20A, 20B, 20C has its respective connector 22A, 22B, 22C. Physically, this arrangement increases the hazards associated with downloading the information from a single logging device. That is, using this method to download the data from the logging devices requires multiple cables strewn about the drilling table 16. The danger created by the download cables 20A, 20B, 20C is increased by the fact that some of the logging devices 12 may be many feet in length and therefore the download cable 20, when connected to an uppermost logging device, e.g. 12A, would be draped either down to the drilling table 16 or to the breakout box 15 when a lower most logging device connector becomes accessible for connection thus creating tripping hazards.
Based on the foregoing, it would be desirable to have a method and device that eliminates the need for a download cable, and in the case of multiple logging devices, multiple download cables, and which further addresses the safety issues generally associated with downloading data from logging devices on a drilling rig or drilling platform.
The problems noted above are solved in large part by a stand-alone data download device. In one embodiment, the data download device electrically couples to a LWD tool and downloads logging data stored in memory of the LWD tool to memory within the data download device. After the information is exchanged between the LWD tool and the data download device, the data download device can be de-coupled from the LWD tool and physically carried to a location near the surface computer where logging information, now contained in memory of the data download device, can be read by the surface computer. In the situation where multiple logging devices exist on the drill string, multiple data download devices could be used such that substantially simultaneous downloading could occur from the logging devices.
In another embodiment of the invention the data download device includes a radio frequency (RF) transmitter/receiver and the surface computer likewise has a RF transmitter/receiver. Therefore, the data download device and the surface computer could communicate while the data download device is electrically coupled to the logging device. In this embodiment it is envisioned that the RF link is used for either relaying data extracted from the logging device, or, is used as a control and monitoring feature whereby the surface computer initiates and monitors downloads between the LWD tool and the data download device.